The availability of all-silicon-based optoelectronic integrated circuit (OEIC) technology promises to revolutionize the optoelectronic industry and significantly impact a wide range of both military and commercial applications. One such area of impact is multi-chip module interconnectivity. Silicon-based OEICs will not only solve resistivity and high-capacitance problems by replacing electron transport with photons, they will also provide new functionality, such as circuit-level image processing. Silicon-based OEICs will also provide cost inroads to commercial markets as high-volume silicon processes enjoy economies of scale unparalleled by other electronic or optoelectronic materials technologies. Furthermore, silicon-based OEICs are expected to provide new functionality such as circuit-level image processing.
There are four technologies required to make silicon-based OEICs a reality: (1) detectors; (2) waveguides; (3) modulators and (4) emitters. While there has been considerable progress in the first three areas, a lack of an appropriate silicon-based light-emitting device, particularly a silicon-based laser, has greatly hindered the development of fully integrated silicon-based OEIC technology.
Most work to date on silicon-based OEICs has been based on III-V materials. However, post-ultra-large-scale integrated (ULSI) circuit work will likely continue to use silicon substrates because of low material costs, high mechanical strength, good thermal conductivity, and the highly developed processing methods available for silicon. One approach to integrating optical and digital electronics is to integrate III-V materials using epitaxially grown III-V layers for selected regions on silicon substrates. Although laser action from III-V layers grown epitaxially on silicon has been demonstrated, progress in this area has been limited by material quality problems resulting from the large lattice and thermal expansion mismatch between the two systems and incompatibilities between III-V material and silicon processing.
Reduced cavity size has been found to significantly affect laser characteristics for silicon-based lasers. When the cavity length is comparable to the wavelength of the cavity-defined radiation, cancellation of spontaneous emissions, zero-threshold lasing and enhanced gain may be achieved. The degree of gain enhancement is determined by the coherent length of the spontaneously emitted radiation. Gain enhancement has been predicted to increase more than five fold in III-V semiconductor microcavities as the emission linewidth decreases from 100 nm to 30 nm.
As result, there is a need for an appropriate silicon-based, light-emitting device that produces photoluminescence emissions and that overcomes material quality problems resulting from large lattice and thermal expansion mismatches between III-V layers and incompatibilities between III-V and silicon processing.
There is a further need for a method to produce photoluminescence emissions from a silicon-based gain medium that does depend on the crystalline quality of the gain medium.